Sporicidal activity of tertiary butyl hydroperoxide

Tertiary butyl hydroperoxide (t-BOOH) was found to be sporicidal for Bacillus megaterium ATCC19213. Sporicidal action was very temperature dependent, and the potency of t-BOOH increased about tenfold for each increase in temperature of 15 °C over the range from 30° to 70 °C. At still higher temperatures, heat and molar levels of t-BOOH were mutually potentiating for killing. Vegetative cells and germinated spores were some thousand times less resistant to t-BOOH than dormant spores. The order of resistance for spores was: Bacillus stearothermophilus ATCC7953 > Bacillus subtilis var. niger = Bacillus megaterium ATCC33729 > Bacillus megaterium ATCC19213. Killing was not enhanced by decoating and occurred without germination or loss of refractility of the spores. Spore resistance to t-BOOH was lower at more acid pH values and was decreased also by demineralization. Spores could be protected by the chelator o-phenanthroline, especially in association with Fe²⁺. Overall, it seemed that killing was associated with nonmetabolic formation of alkyl peroxyl radicals, which are thought to be responsible for killing of vegetative cells by organic hydroperoxides.Abbreviation A-BOOH tertiary butyl hydroperoxide